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United States Patent |
5,723,084
|
Shin
|
March 3, 1998
|
Flash spinning process
Abstract
Olefin/carbon monoxide alternating polymers are flash-spun to form
plexifilamentary products, pulp products, and foam products from alcohol
or halogenated hydrocarbon solvents having 1 to 3 carbon atoms.
Inventors:
|
Shin; Hyunkook (Wilmington, DE)
|
Assignee:
|
E. I. du Pont de Nemours and Company (Wilmington, DE)
|
Appl. No.:
|
612713 |
Filed:
|
March 8, 1996 |
Current U.S. Class: |
264/205 |
Intern'l Class: |
D01D 005/11 |
Field of Search: |
264/13,205,211,211.14
|
References Cited
U.S. Patent Documents
3081519 | Mar., 1963 | Blades et al. | 57/248.
|
3227664 | Jan., 1966 | Blades et al. | 264/205.
|
3584090 | Jun., 1971 | Parrish | 264/45.
|
3637458 | Jan., 1972 | Parrish.
| |
3835123 | Sep., 1974 | Nozaki | 528/392.
|
3851023 | Nov., 1974 | Brethauer | 26/205.
|
3914391 | Oct., 1975 | Nozaki | 423/364.
|
4608089 | Aug., 1986 | Gale et al. | 524/8.
|
5250237 | Oct., 1993 | Shin | 264/13.
|
5279776 | Jan., 1994 | Shah | 264/12.
|
5403531 | Apr., 1995 | Rutten | 264/204.
|
Foreign Patent Documents |
332 975 | Jul., 1989 | EP.
| |
360358 | Mar., 1990 | EP.
| |
456 306 | Nov., 1991 | EP.
| |
Primary Examiner: Tentoni; Leo B.
Claims
What is claimed is:
1. A process for the production of flash-spun plexifilamentary film-fibril
strands of a high molecular weight alternating copolymer of ethylene and
carbon monoxide or a high molecular weight alternating copolymer having
alternating polymerized units of carbon monoxide and at least two
different olefin units one of which is ethylene, and the remainder are
selected from the group consisting of propylene, butene, pentene, hexene,
heptene, octene, nonene, decene, dodecene, styrene, methyl acrylate,
methyl methacrylate, vinyl acetate, undecenoic acid, undecenol,
6-chlorohexene, N-vinylpyrrolidone, and the diesters of vinylphosphonic
acid in which a majority of the olefin units are ethylene units which
comprises forming a spin solution of said alternating copolymer in a
solvent having an atmospheric boiling point between 0.degree. C. and
210.degree. C., and selected from the group consisting of alcohols and
halogenated hydrocarbons having 1 to 3 carbon atoms and spinning said spin
solution at a pressure that is greater than the autogenous pressure of the
spin solution into a region of substantially lower pressure and at a
temperature at least 50.degree. C. higher than the atmospheric boiling
point of the solvent to form plexifilamentary film-fibril strands of said
alternating copolymer.
2. The process of claim 1 in which the alcohol is selected from the group
consisting of n-pentafluoropropanol, trifluoroethanol,
2,2,3,3,-tetrafluoro-1-propanol, hexafluoroisopropanol,
heptafluoro-1-butanol, cyclohexanol, 1-methyl cyclohexanol,
cis-2-methylcyclohexanol, trans-2-methylcyclohexanol,
cis-3-methylcyclohexanol, trans-3-methylcyclohexanol, benzyl alcohol,
phenol, and m-cresol.
3. The process of claim 1 in which the alcohol is selected from the group
consisting of n-pentafluoropropanol, trifluoroethanol,
2,2,3,3,-tetrafluoro-1-propanol, hexafluoroisopropanol, and
heptafluoro-1-butanol.
4. The process of claim 1 in which the alcohol is selected from the group
consisting of cyclohexanol, 1-methyl cyclohexanol,
cis-2-methylcyclohexanol, trans-2-methylcyclohexanol,
cis-3-methylcyclohexanol, trans-3-methylcyclohexanol, benzyl alcohol,
phenol, and m-cresol.
5. The process of claim 1 in which the spin solution contains more than one
of the alcohols selected from the group consisting of
n-pentafluoropropanol, trifluoroethanol, 2,2,3,3,-tetrafluoro-1-propanol,
hexafluoroisopropanol, heptafluoro-1-butanol, cyclohexanol, 1-methyl
cyclohexanol, cis-2-methylcyclohexanol, trans-2-methylcyclohexanol,
cis-3-methylcyclohexanol, trans-3-methylcyclohexanol, benzyl alcohol,
phenol and m-cresol.
6. The process of claim 1 in which the alcohol is n-pentafluoropropanol.
7. The process of claim 1 where the alternating copolymer consists of
polymerized ethylene units and carbon monoxide units.
8. The process of claim 1 in which the atmospheric boiling point of the
solvent is between 0.degree. and 100.degree. C.
9. The process of claim 1 in which the solution is spun at a temperature
between 200.degree. C. and 300.degree. C. and at a pressure of greater
than 500 psig.
10. The process of claim 1 wherein the solvent is methylene chloride.
Description
FIELD OF THE INVENTION
This invention relates to the flash-spinning of high molecular weight
alternating copolymers of olefin units and carbon monoxide units, where
the olefin units are either all ethylene units or are mostly ethylene
units, and the remainder of the olefin units are one or more units
selected from the group consisting of propylene, butene, pentene, hexene,
heptene, octene, nonene, decene, dodecene, styrene, methyl acrylate,
methyl methacrylate, vinyl acetate, undecenoic acid, undecenol,
6-chlorohexene, N-vinylpyrrolidone, and the diesters of vinylphosphonic
acid. These copolymers are flash spun from a solvent having a boiling
point between 0.degree. and 210.degree. C. and selected from the group
consisting of alcohols and halogenated hydrocarbons having 1 to 3 carbon
atoms. A preferred class of solvents are halogenated alcohols and a most
preferred class of solvents are fluorinated alcohols.
BACKGROUND OF THE INVENTION
Alternating high molecular weight copolymers of olefin units and carbon
monoxide are known: see U.S. Pat. Nos. 3,914,391 and 3,835,123 to Nozaki.
Published European Patent Application 0,360,358 discloses forming fibers
from alternating high molecular weight copolymers of olefin units and
carbon monoxide by solution or gel-spinning of a solution of the copolymer
through a spinning aperture. The solvent employed are
hexafluoroisopropanol, m-cresol, and mixtures thereof.
Flash-spinning of olefin polymers to produce non-woven sheets is practiced
commercially and is the subject of numerous U.S. Patents including
Brethauer et al. U.S. Pat. No. 3,851,023.
Flash-spinning of olefin polymers to produce pulp-like products from
polymer solutions is disclosed in U.S. Pat. 5,279,776 to Shah. Pulp
products can also be produced by disk refining (grinding) of
olefin-polymer plexifilaments.
Flash-spinning of olefin polymers to produce microcellular and
ultra-microcellular foam products from polymer solutions is disclosed in
U.S. Pat. No. 3,227,664 to Blades et al. and U.S. Pat. No. 3,584,090 to
Parrish.
SUMMARY OF THE INVENTION
The present invention is a process for the production of flash-spun
plexifilamentary film-fibril strands or foam or pulp of a high molecular
weight alternating copolymer of ethylene and carbon monoxide or a high
molecular weight alternating copolymer having alternating polymerized
units of carbon monoxide and at least two different olefin units one of
which is ethylene, and the remainder are selected from the group
consisting of propylene, butene, pentene, hexene, heptene, octene, nonene,
decene, dodecene, styrene, methyl acrylate, methyl methacrylate, vinyl
acetate, undecenoic acid, undecenol, 6-chlorohexene, N-vinylpyrrolidone,
and the diesters of vinylphosphonic acid in which a majority of the olefin
units are ethylene units, which comprises forming a spin solution of said
alternating copolymer in a solvent having an atmospheric boiling point
between 0.degree. C. and 210.degree. C., preferably between 0.degree. C.
and 170.degree. C., and selected from the group consisting of alcohols and
halogenated hydrocarbons having 1 to 3 carbon atoms and spinning said spin
solution at a pressure that is greater than the autogenous pressure of the
spin solution into a region of substantially lower pressure, and at a
temperature at least 50.degree. C. higher than the atmospheric boiling
point of the solvent.
In its most preferred form in the process of the present invention the
solvent is selected from the group consisting of n-pentafluoropropanol,
trifluoroethanol, 2,2,3,3,-tetrafluoro-1-propanol, hexafluoroisopropanol,
heptafluoro-1-butanol, cyclohexanol, 1-methyl cyclohexanol,
cis-2-methylcyclohexanol, trans-2-methylcyclohexanol,
cis-3-methylcyclohexanol, trans-3-methylcyclohexanol, benzyl alcohol,
phenol, and m-cresol. The spin solution may contain more than one of said
alcohols.
In one preferred embodiment the alternating copolymer consists of
polymerized ethylene units and carbon monoxide units.
The present invention is also a spin solution of a high molecular weight
alternating copolymer of ethylene and carbon monoxide or a high molecular
weight copolymer having alternating polymerized units of carbon monoxide
and at least two different olefin units one of which is ethylene, and the
remainder are selected from the group consisting of propylene, butene,
pentene, hexene, heptene, octene, nonene, decene, dodecene, styrene,
methyl acrylate, methyl methacrylate, vinyl acetate, undecenoic acid,
undecenol, 6-chlorohexene, N-vinylpyrrolidone, and the diesters of
vinylphosphonic acid in which a majority of the polymerized olefin units
are ethylene units, in an alcohol having an atmospheric boiling point
between 0.degree. C. and 210.degree. C.
In one preferred embodiment the alcohol of the spin solution is a
fluorinated alcohol and is preferably selected from the group consisting
of n-pentafluoropropanol, trifluoroethanol,
2,2,3,3,-tetraflouro-1-propanol, hexafluoroisopropanol, and
heptafluoro-1-butanol.
Usually in the spin solution the concentration of the copolymer in the
solution is between 5 and 70 wt. % of the solution, preferably between 5
and 35 wt. % of the solution.
Normally, the solution is spun at a temperature between 200.degree. C. and
300.degree. C. (preferably 215.degree. to 250.degree. C.) and at a
pressure of greater than about 500 psig.
The invention is also a plexifilament of a high molecular weight
alternating copolymer of ethylene and carbon monoxide or a high molecular
weight alternating copolymer having alternating polymerized units of
carbon monoxide and at least two different olefin units one of which is
ethylene, and the remainder are selected from the group consisting of
propylene, butene, pentene, hexene, heptene, octene, nonene, decene,
dodecene, styrene, methyl acrylate, methyl methacrylate, vinyl acetate,
undecenoic acid, undecenol, 6-chlorohexene, N-vinylpyrrolidone, and the
diesters of vinylphosphonic acid in which a majority of the polymerized
olefin units are ethylene units.
The invention is also a foam of a high molecular weight alternating
copolymer of ethylene and carbon monoxide or a high molecular weight
alternating copolymer having polymerized units of carbon monoxide and at
least two different polymerized olefin units one of which is ethylene, and
the remainder are selected from the group consisting of propylene, butene,
pentene, hexene, heptene, octene, nonene, decene, dodecene, styrene,
methyl acrylate, methyl methacrylate, vinyl acetate, undecenoic acid,
undecenol, 6-chlorohexene, N-vinylpyrrolidone, and the diesters of
vinylphosphonic acid in which a majority of the polymerized olefin units
are ethylene units.
The invention is also a pulp of high molecular weight alternating copolymer
of ethylene and carbon monoxide or a high molecular weight alternating
copolymer having polymerized units of carbon monoxide and at least two
different olefin units one of which is ethylene, and the remainder are
selected from group consisting of propylene, butene, pentene, hexene,
heptene, octene, nonene, decene, dodecene, styrene, methyl acrylate,
methyl methacrylate, vinyl acetate, undecenoic acid, undecenol,
6-chlorohexene, N-vinylpyrrolidone, and the diesters of vinylphosphonic
acid in which a majority of the polymerized olefin units are ethylene
units.
The plexifilaments of the invention may be formed into non-woven sheets
(fabric) by the procedure disclosed in Brethauer et al. U.S. Pat. No.
3,851,023.
The pulps of the invention may be wet laid to form paper-like sheets
(fabric) by the use of conventional paper-making processes.
DETAILED DESCRIPTION
In the alternating polymers of carbon monoxide and olefin, carbon monoxide
is approximately every other unit of the polymer, and an olefin unit is
every other unit. In the preferred embodiment, the olefin units are all
ethylene, but up to 1/4 of the olefin units may be one or more units
selected from the group consisting of propylene, butene, pentene, hexene,
heptene, octene, nonene, decene, dodecene, styrene, methyl acrylate,
methyl methacrylate, vinyl acetate, undecenoic acid, undecenol,
6-chlorohexene, N-vinylpyrrolidone, and the diesters of vinylphosphonic
acid.
The term "autogenous pressure" is the natural vapor pressure of the spin
mixture at a given temperature.
The morphology of flash spun fibers depends on the polymer concentration
and spin conditions used. To obtain plexifilaments, relatively low polymer
concentrations (e.g., less than about 35 wt. %) are normally used, and, in
addition, spin temperatures used must be high enough to provide rapid
flashing of the solvent. Well fibrillated plexifilaments are usually
obtained when the spin temperature used is between the critical
temperature of the spin liquid and 40.degree. C. below the critical
temperature.
Microcellular foams are usually prepared at relatively high polymer
concentrations and relatively low spin temperatures and pressures.
Nucleating agents, such as fumed silica and kaolin, are usually added to
the spin mix to facilitate solvent flashing and to obtain uniform small
size cells. Microcellular foams can be obtained in a collapsed form or in
a fully or partially inflated form. For many polymer/solvent systems,
microcellular foams will tend to collapse after exiting the spinning
orifice as the solvent vapor condenses inside the cells and/or diffuses
out of the cells. To obtain low density inflated foams, inflating agents
are usually added to the spin liquid. Inflating agents to be used should
have permeability coefficient for diffusion through the cell walls less
than that of air so that they can stay inside the cells for a long period
of time while allowing air to diffuse into the cells to keep the cells
inflated. Osmotic pressure will cause air to diffuse into the cells.
Suitable inflating agents that can be used include low boiling halocarbons
such as hydrochlorofluorocarbons, hydrofluorocarbons, chlorofluorocarbons,
and perfluorocarbons (e.g., octafluorocyclobutane); inert gases such as
carbon dioxide, and nitrogen; low boiling hydrocarbon solvents such as
butane and isopentane; and other low boiling organic solvents and gases.
The atmospheric boiling points of these inflatants are typically between
the room temperature and -50.degree. C. For inert gases the boiling points
will, of course, be much lower than -50.degree. C.
Microcellular foam fibers are normally spun from a round cross section
spinneret. However, an annular die similar to the ones used for blown
films can be used to make microcellular foam sheets. For fully inflated
foams, as-spun fibers or as-extruded foam sheets can be post-inflated by
immersing them in a solvent containing dissolved inflatants. Inflatants
will diffuse into the cells due to the plasticizing action of the solvent.
Once dried, the inflatants will stay inside the cells and air will diffuse
into the cells due to osmotic pressure to keep the microcellular foams
inflated.
The microcellular foams of this invention have densities between 0.005 and
0.50 gm/cc. Their cells are generally of a polyhedral shape and their
average cell size is less than about 300 microns, preferably less than
about 150 microns. Their cell walls are typically less than about 3
microns, preferably less than about 2 microns in thickness.
The pulps of this invention can be produced by disc refining flash spun
plexifilaments as disclosed in U.S. Patent 4,608,089 to Gale & Shin.
Alternatively, they can be prepared directly from polymer solutions by
flash spinning using a device similar to the one disclosed in U.S. Pat.
No. 5,279,776 to Shah.
The pulps made by this invention are plexifilamentary film-fibrils in
nature and can have a three dimensional network structure. However, they
are relatively short in length and have small dimensions in the transverse
direction. Their average length is less than about 3 mm and their average
diameter is less than about 200 microns, preferably less than about 50
microns. They have relatively high surface area; greater than about 1
square meter per gram when determined by BET.
The olefin/carbon monoxide alternating copolymers, especially
ethylene/carbon monoxide alternating copolymers, are soluble in the cyclic
alcohols and the fluorinated alcohols listed above at elevated
temperatures and pressures.
Ideally, the solvents to be used for flash spinning should have high enough
solvent power to dissolve polymer to give a homogeneous single-phase
solution at the temperature and pressure used for mixing. However, in some
case, the solvents to be used do not have to have such a high solvent
power so long as their solvent power is high enough to give a reasonably
stable two-phase dispersion suitable for flash spinning. In this case,
both mixing and spinning will be performed below the cloud point pressure,
which is the minimum pressure needed to obtain a single-phase solution at
any given temperature. Methanol, ethanol, and propanols belong to this
category. These alcohols do not have sufficient solvent power to dissolve
ethylene/carbon monoxide homopolymer at pressures less than about 5000
psig, but their solvent power is high enough to give a relatively stable
dispersion that can be flash spun into well fibrillated plexifilaments.
The most satisfactory solvents of halogenated hydrocarbon type are
dichloromethane and monobromomonochloromethane.
Preparation of Alternating Ethylene/Carbon Monoxide Copolymer
The catalyst employed was obtained by adding the contents of two bottles to
an autoclave as described below.
Bottle #1 contained:
Pd(OAc)2 i.e., palladium diacetate (0.44 g, 2.0 mmol)
1,3-bis(diphenylphosphino)propane (0.98 g, 2.4 mmol)
Methanol (600 mL)
Toluene (400 mL)
Bottle #2 contained:
Methanol (500 mL)
Toluene (100 mL)
Toluene sulfonic acid (7.6 g, 40 mmol)
Polymerization Conditions
A 1 gal Hastalloy autoclave was sealed and purged with nitrogen. After
purging was complete, the contents of bottle #1 were added through a
cannula. The contents of bottle #2 were then added. The autoclave was then
cooled to 0.degree. C. and was pressured to 850 psi with a 1:1 molar ratio
of ethylene and carbon monoxide. The temperature and pressure were
maintained for 48 hours. The pressure was vented to atmospheric pressure.
The autoclave was warmed to room temperature and opened. The produce was a
greenish-tinted solvent and off-white chunks of polymer.
Polymer Workup
Most of the supernatent solvent was decanted. The soft, white chunks of
polymer were placed in methanol in a blender and homogenized. The
resulting slurry was then filtered using vacuum. The polymer was then
washed sequentially with acetone (1 gal.) water (1 L) and methanol (2 L).
The very white powdery polymer was then dried under vacuum.
Yield
142 g.
The Polymer had the Following Properties
Number average molecular weight measured by Nuclear Magnetic Resonance
technique of endgroups: 101,000.
Number average molecular weight measured by Gel permeation chromatography
in hexafluoroisopropanol: 42,600.
Weight average molecular weight measured by Gel permeation chromatography
in hexafluoroisopropanol: 141,000.
The apparatus and process for carrying out the examples is as described in
U.S. Pat. No. 5,250,237 at column 10 and following. This patent is hereby
incorporated by reference.
Test Methods
The tenacity of the flash-spun strand is determined with an Instron
tensile-testing machine. The strands are conditioned and tested at
70.degree. F. and 65% relative humidity. The sample is then twisted to 10
turns per inch and mounted in jaws of the Instron Tester. A 2-inch gauge
length and an elongation rate of 100% per minute are used. The tenacity
(T) at break is recorded in grams per denier.
Denier of the strand is determined from the weight of a 18 cm sample length
of the strand.
Elongation of the flash-spin strand is measured as elongation at break and
is reported as a percentage.
EXAMPLE 1
15 wt. % of the ethylene/carbon monoxide copolymer prepared as described
above was dissolved in n-pentafluoropropanol at 240.degree. C. at a
maximum pressure of 2500 psig with a pressure differential between the two
mixing compartments as described in U.S. Pat. No. 5,250,237 of 200 psig
for 15 minutes.
The solution was then spun at 1100 psig at 240.degree. C. through a thirty
mil diameter spinneret orifice. The spin lasted approximately one second.
The product was a plexifilament having a denier of 306 grams, a tenacity
of 0.9 grams per denier, and an elongation at break of 42%. The product
was well fibrilated and strong.
EXAMPLE 2
25 wt. % of the ethylene/carbon monoxide copolymer prepared as described
above was dissolved in hexafluoroisopropanol at 230.degree. C. at a
maximum pressure of 2000 psig with a pressure differential between the two
mixing compartments of 200 psig for 45 minutes.
The solution was then spun at 775 psig at 231.degree. C. through a thirty
mil diameter spinneret orifice. The spinning time was approximately 1.5
seconds. The product was a foam of good quality.
EXAMPLE 3
An alternating ethylene/carbon monoxide copolymer having number and weight
average molecular weights as determined by the gel permeation
chromatography of 14,700 and 22,500, respectively, was prepared. 65 wt. %
of the polymer was dissolved in n-pentafluoropropanol at 230.degree. C. at
a maximum pressure of 2000 psig with a pressure differential between the
two mixing compartments of 300 psig for one hour. The solution was spun at
230.degree. C. through a 30 mil diameter hole spinneret using 500 psig
accumulator pressure. Actual pressure during spinning was about 400 psig.
Uniform microcellular foam was obtained.
EXAMPLE 4
An intermediate MW ethylene/carbon monoxide polymer having number average
MW of 25,900 and weight average MW of 73,300 (determined by gel permeation
chromatography) was prepared by using a procedure similar to the one
described before. 20 wt. % of the polymer was mixed with methanol at
205.degree. C. and 3000 psig for 10 min. The mixing time was reduced to
minimize polymer degradation. The two-phase dispersion thus prepared was
spun using accumulator pressure of 2000 psig. Actual spin pressure
measured during spinning was about 1800 psig. The product was a
plexifilament having a denier of 691, a tenacity of 0.73 grams per denier,
and an elongation at break of 101%. In a separate experiment conducted
with a view cell, it was determined that the cloud point pressure for this
system at 205.degree. C. is higher than the 3000 psig mixing pressure
used, and therefore, the spin mix, which was prepared, was a two-phase
dispersion rather than a single-phase solution.
EXAMPLE 5
A 20 wt. % mixture of the same polymer as used in Example 4 and methylene
chloride was prepared and mixed at 215.degree. C. at 3100 psig. The
mixture was spun at 215.degree. C. using a accumulator pressure of 2200
psig and an actual spin pressure of 750 psig. The product had a denier of
335, a tenacity of 1.35 grams per denier, and an elongation at break of
64%.
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